Hongying Zhuo

Cooperative and Diminutive Effects of Pnicogen Bonds and Cation–π Interactions

The interplay between pnicogen bonds and cation-π interactions has been investigated at the MP2/aug-cc-pVDZ level. Interesting cooperative and diminutive effects are observed when pnicogen bonds and cation-π interactions coexist in the same complex. These effects have been analyzed in terms of the structural, energetic, and charge-transfer properties of the complexes. The variations in electron density at critical points of the intermolecular bond have been used to analyze bond strengthening or weakening. The nature of the interactions and the mechanisms of cooperative and diminutive effects have been studied by means of symmetry-adapted perturbation theory and molecular electrostatic potentials.

Complexes between hypohalous acids and phosphine derivatives. Pnicogen bond versus halogen bond versus hydrogen bond

The complexes of HOBr:PH2Y (Y=H, F, Cl, Br, CH3, NH2, OH, and NO2), HOCl:PH2F, and HOI:PH2F have been investigated with ab initio calculations at the MP2/aug-cc-pVTZ level. Four types of structures (1, 2, 3a, and 3b) were observed for these complexes. 1 is stabilized by an O⋯P pnicogen bond, 2 by a P⋯X halogen bond, 3a by a H⋯P hydrogen bond and a P⋯X pnicogen bond, and 3b by H⋯P and H⋯Br hydrogen bonds. Their relative stability is related to the halogen X of HOX and the substituent Y of PH2Y. These structures can compete with interaction energy of -10.22∼-29.40 kJ/mol. The HO stretch vibration shows a small red shift in 1, a small irregular shift in 2, but a prominent red shift in 3a and 3b. The XO stretch vibration exhibits a smaller red shift in 1, a larger red shift in 2, but an insignificant blue shift in 3a and 3b. The PY stretch vibration displays a red shift in 1 but a blue shift in 2, 3a, and 3b. The formation mechanism, stability, and properties of these structures have been analyzed with molecular electrostatic potentials, orbital interactions, and non-covalent interaction index.

The dual role of pnicogen as Lewis acid and base and the unexpected interplay between the pnicogen bond and coordination interaction in H3N⋯FH2X⋯MCN (X = P and As; M = Cu, Ag, and Au)

Ternary systems H3N⋯FH2X⋯MCN (X = P and As; M = Cu, Ag, and Au) as well as the corresponding pnicogen-bonded and coordination-bonded binary systems have been studied. The X atom acts as an electron acceptor and a donor in the pnicogen bond and coordination interaction, respectively, simultaneously playing both roles in the ternary complexes. Electrostatic interaction and charge transfer make dominant contributions to the stability of the pnicogen bond, while the coordination interaction results mainly from electrostatic and polarization interactions. Relativistic effects especially for the Au atom lead to some irregularity in interaction energy and the binding distance in the coordination interactions. In the ternary complex, the stronger coordination interaction strengthens the weaker pnicogen bond, while the pnicogen bond weakens the coordination interaction. The weakening of the coordination interaction was evidenced by the longer binding distance, lower electron density at the bond critical point, and smaller charge transfer. The change in the pnicogen bond and coordination interaction in the ternary complex has been rationalized with the analyses of the electrostatic potentials, occupancy on the lone pair of the X atom as well as the orbital interactions.

Halogen bonds with N-heterocyclic carbenes as halogen acceptors: a partially covalent character

N-heterocyclic carbenes (NHCs) are important ligands in organometallic catalytic reactions. This study focuses on the halogen bonds with NHCs as the electron donors. The results show that NHCs are better electron donors in halogen bonds. Our interest is how to make a halogen bond having a partially covalent property, which depends on the strength of halogen bonding. The covalent property of halogen bonding is related to the nature of the halogen donor. Iodine is favourable to form a halogen bond with covalent property than chlorine and bromine. The covalent property of halogen bond is greatly affected by substituents. Strong electron-donating groups in NHCs could reinforce the covalent attribute of bromine bonding, whereas strong electron-withdrawing groups in NHCs make iodine bonding lose the covalent nature. The covalent property of halogen bond is further heightened through the cooperative effect between the carbene–halogen bond and another interaction. This covalent property results in a much short binding distance and a prominent bond elongation. The covalent property of halogen bond has been analysed with the energy density, electron local function, and electron density shifts.

Competition between hydrogen bonds and halogen bonds in complexes of formamidine and hypohalous acids

Quantum chemical calculations have been per-formed for the complexes of formamidine (FA) and hypohalous acid (HOX, X = F, Cl, Br, I) to study their structures, properties, and competition of hydrogen bonds with halogen bonds. Two types of complexes are formed mainly through a hydrogen bond and a halogen bond, respectively, and the cyclic structure is more stable. For the F, Cl, and Br complexes, the hydrogen-bonded one is more stable than the halogen-bonded one, while the halogen-bonded structure is favorable for the I complexes. The associated H-O and X-O bonds are elongated and exhibit a red shift, whereas the distant ones are contracted and display a blue shift. The strength of hydrogen and halogen bonds is affected by F and Li substitutents and it was found that the latter tends to smooth differences in the strength of both types of interactions. The structures, properties, and interaction nature in these complexes have been understood with natural bond orbital (NBO) and atoms in molecules (AIM) theories.

Theoretical study of the cooperative effects between the triel bond and the pnicogen bond in BF3···NCXH2···Y (X = P, As, Sb; Y = H2O, NH3) complexes

The interplay between the triel bond and the pnicogen bond in BF3···NCXH2···Y (X = P, As, Sb; Y = H2O, NH3) complexes was studied theoretically. Both bonds exhibited cooperative effects, with shorter binding distances, larger interaction energies, and greater electron densities found for the ternary complexes than for the corresponding binary ones. The cooperative effects between the triel bond and the pnicogen bond were probed by analyzing molecular electrostatic potentials, charge transfer, and orbital interactions. The results showed that the enhancement of the triel bond can mainly be attributed to the electrostatic interaction, while the strengthening of the pnicogen bond can be ascribed chiefly to the electrostatic and orbital interactions. In addition, the origins of both the triel bond and the pnicogen bond were deduced via energy decomposition.

Mutual influence between covalent and noncovalent interactions in H3N–MCN–XF (X = H, Li, Cl, Br; M = Ag, Cu, Au)

The interplay between covalent and noncovalent interactions has been investigated in H3N–MCN–XF (X = H, Li, Cl, Br; M = Ag, Cu, Au) complexes using ab initio calculations at the MP2 level of theory. The coinage metal as a substituent has an irregular enhancing effect (Au < Cu < Ag) on the strength of noncovalent interaction in MCN–XF, while the covalent interaction in H3N–MCN becomes stronger with the reverse order. Interesting cooperativity effects were observed when covalent and noncovalent interactions coexist in the same complex, and they become more prominent for the stronger covalent and noncovalent interactions. These effects have been characterised in detail with the structural, spectroscopic, energetic, and charge transfer features of the complexes.

Novel non-covalent interactions involved with the Al13M cluster (M = Li, Na, K, Cu, Ag, Au)

The complexes of Al13M cluster (M = Li, Na, K, Cu, Ag, Au) and Lewis bases NH3, H2O, C6H6, and HLi have been predicted and characterised. The results showed that the cluster Al13M forms the alkali-bonding or coinage metal-bonding interaction through M with these Lewis bases. These complexes exhibit some similarities and differences in the structures, properties, and nature with conventional molecules. The formation of these interactions has a negligible or small effect on the structures of Al13M. This study combines the cluster Al13M with non-covalent interactions, which is of great importance in supramolecular chemistry.

Influence of the nature of hydrogen halides and metal cations on the interaction types between borazine and hydrogen halides.

AbstractThe interactions between the H atom of borazine and hydrogen halide (HX, X = F, Cl, Br, and I) have been studied systematically. Four structures (a, b, c, and d) have been observed. The cyclic structure a is combined through a NH···X hydrogen bond and a BH···HX dihydrogen bond, a NH···X hydrogen bond and a BH···X halogen-hydride interaction are responsible for the cyclic structure b, structures c and d are maintained by a dihydrogen bond and a halogen-hydride interaction, respectively. Structures a and b are stable in energy, while structures c and d are unstable in energy. Structures a and b can transform each other through structure c or d. The interaction mode and strength are related to the nature of HX. The cation-π interaction of borazine with Li+ and Mg2+ causes a change in the interaction mode in structures a and b, and has an enhancing effect on the interaction strength in a and b. FigureThe interaction modes between the H atom of borazine and hydrogen halide (HX, X = F, Cl, Br, and I) can be regulated by the nature of HX and cations.